LIPID MAPS shorthand notation

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Enforces the LIPID MAPS shorthand for mass-spectrometry-derived lipid names. The punctuation carries meaning: the separator between chains, the prefixes, and the hydroxyl suffix each encode exactly how much structure the measurement resolved. Apply whenever you write, normalize, or correct a lipid species name for a results table, figure, or report.

Rules

1. Class then a single space then the composition. Write Class C:DB — the class abbreviation,

ONE space, then carbons:double-bonds. Never fuse them (PC34:1) and never wrap the composition in parentheses (PC(34:1)). C is total acyl/radyl carbons, DB total carbon-carbon double bonds.

1. The chain separator states what was measured — this is the core of the convention:

• Chains identified but the sn-1 / sn-2 assignment NOT determined → join with an underscore _.
• sn-1 / sn-2 genuinely assigned → join with a slash /, sn-1 chain written first.
• Only claim / when a regiochemistry-resolving method was run (electron-activated dissociation,

ozone-based, ultraviolet photodissociation, or an enzymatic assay). Ordinary collisional dissociation (CID) does NOT resolve sn — its acyl-loss intensities are a biased blend, not a structure readout — so default a CID-only name to _. When in doubt, drop a level.

1. Sum-composition (species) level. If the individual chains were never resolved, stop at

Class C:DB (e.g. PC 34:1). Do not invent chains, an underscore, or a slash.

1. Double-bond position + geometry go in ONE pair of parentheses right after the chain: each a

locant number followed by Z (cis) or E (trans), comma-separated for multiple bonds — 18:2(9Z,12Z). Never cis/trans words, 9c/9t, a Δ delta symbol, or an n-/omega descriptor.

1. Ether and plasmalogen linkages use a radyl prefix directly before the chain: alkyl ether = O-,

vinyl-ether plasmalogen = P- (e.g. PC O-16:0/18:1, PE P-16:0/20:4). The vinyl-ether double bond is implied by P- and is NOT counted in the chain's DB.

1. Sphingoid-base hydroxylation is a functional-group suffix ;O<n> on the sphingoid part:

;O2 for a dihydroxy base (sphingosine/sphinganine), ;O3 for a trihydroxy base (phytosphingosine). The old d/t prefixes are deprecated — write Cer 18:1;O2/24:0, not Cer d18:1/24:0.

1. Single-chain and other classes. A lyso-lipid carries one acyl chain and no separator

(LPC 18:1). Free fatty acids take the FA class token (FA 18:0), cholesteryl/sterol esters CE (CE 18:1). Added oxygens (hydroxyl/epoxide/keto) of unknown position are the same ;O<n> suffix on the affected part (FA 18:1;O = one extra oxygen), consistent with the sphingoid rule.

The same six punctuation rules apply across every lipid category — glycerophospholipids, glycerolipids, sphingolipids, sterols, and fatty acyls — so a name is portable between tools once it conforms.

Worked examples (base default → conforming)

• PC(34:1) (parenthesized export) → PC 34:1
• PC 16:0/18:1 claimed from CID-only data → PC 16:0_18:1 (no sn evidence → underscore)
• PC 16:0/18:1 with EAD sn assignment → PC 16:0/18:1 (slash is licensed)
• Cer d18:1/24:0 (old dihydroxy prefix) → Cer 18:1;O2/24:0
• Cer t18:0/16:0 (old trihydroxy prefix) → Cer 18:0;O3/16:0
• 18:1 cis-9 / 18:1n-9 / 18:1Δ9 → FA 18:1(9Z)
• plasmenyl-PE 18:0/20:4 → PE P-18:0/20:4
• PC(O-16:0/18:1) → PC O-16:0/18:1
• LysoPC 18:1 / 1-oleoyl-LPC → LPC 18:1 (single acyl chain, no separator)
• cholesteryl oleate → CE 18:1 (one acyl chain on the sterol)
• 18:1;OH (9-hydroxy, position unspecified) → FA 18:1;O (functional-group oxygen suffix)

Edge cases & exceptions

• Ether vs plasmalogen at sum level: a sum composition alone cannot distinguish P-34:1 from

O-34:2 (a vinyl ether equals an ether plus one double bond). Report O- unless a vinyl-ether diagnostic ion or acid-lability test confirms P-.

• P- double-bond bookkeeping: because P- implies the enol double bond, P-18:0 and O-18:1

describe the same radyl; count only the additional double bonds under P-.

• Geometry unmeasured: if a double-bond position is known but its geometry is not, give the locant

and omit the letter rather than guessing Z/E.

• Odd or unexpected chains: a name is a claim about evidence, not a guess — never promote a level

(e.g. _ to /) to look more precise.

• Apparent odd-carbon species (e.g. an odd total carbon count) are usually an in-source fragment or a

¹³C-isotope artifact of an even neighbor; do not name one as an intact species without chain confirmation.

• Oxidized-lipid position stated without evidence: use the bare ;O<n> count rather than asserting a

specific hydroxyl/epoxide locant the data did not localize.

Do / Don't

• DO put a single space between class and composition. DON'T wrap it in parentheses.
• DO use _ when the sn assignment is unproven. DON'T emit / without a regiochemistry-resolving method.
• DO write ;O2 / ;O3. DON'T carry the old d / t sphingoid prefixes.
• DO encode double bonds as (9Z) / (9E). DON'T write cis/trans, 9c/9t, Δ9, or n-9.
• DO prefix ether with O- and plasmalogen with P-. DON'T spell out "alkyl", "plasmenyl", or "plasmalogen".

Common mistakes

• Emitting a slash (/) when only the chain composition is known — the single most common overstatement.
• Carrying the deprecated d18:1 / t18:0 sphingoid prefixes instead of ;O2 / ;O3.
• Writing double-bond geometry as cis/trans or with Δ / n- instead of (nZ) / (nE).
• Wrapping the composition in parentheses (PC(16:0/18:1)) or fusing the class to the numbers.
• Inventing individual chains when only the summed composition was measured.

Quick checklist

• ] class + single space + C:DB (no parentheses)
• ] _ unless sn was truly resolved, then / with sn-1 first
• ] sum-composition only when chains unresolved (no invented _//)
• ] (nZ) / (nE) for any double-bond position + geometry
• ] O- ether / P- plasmalogen prefix
• ] ;O2 / ;O3 sphingoid hydroxyl, never d / t